<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      const arr = new Array()
      const date = new Date()
      const fd = new FormData()
      const str = 'a=1&b=2'
      const obj = { a: 1, b: 2 }

      console.log(typeof arr)  // object 检测不出来
      console.log(arr instanceof Array)  // true
      console.log(date instanceof Array) // fasle

      console.log(fd instanceof FormData)  // true
      console.log(str instanceof FormData) // fasle
      console.log(obj instanceof FormData) // fasle
    </script>
  </body>
</html>
